A video encoding apparatus encodes in an encoding process input video frames into an encoded video frame for storage or transmission, to be used in a video decoding apparatus for reconstruction of the stored or transmitted signal in order to obtain a reconstruction of the original video signal. The encoding process enables compression of the original video signal such that the compressed video signal can be stored on a storage medium requiring storage having only a fraction of storage capacity that would be needed if the original input video frames would be stored or can transmit a video signal in a compressed way requiring only limited bandwidth compared to the bandwidth needed to transmit the original video signal.
In order to enhance the video encoding process, modern video encoding/decoding standards, such as H.264, use intra-frame prediction. In intra-frame prediction blocks of pixels are reconstructed using surrounding reconstructed pixels from a frame currently under reconstruction. Knowledge of surrounding pixels is used to create a prediction of a new block in an appropriate direction. More specifically, the surrounding pixels of this yet to be created block are extended in a given direction to create this block, for example by extrapolating in this direction. The direction is indicated by an intra-frame prediction mode. Predicted blocks generated by different intra-frame prediction modes may be evaluated according to selection criteria and a best intra-frame prediction mode may be selected. Once an intra-frame prediction mode is established, it will be coded and added to the encoded video frame.
In the art of video encoding/decoding intra-frame prediction is performed using a predetermined set of possible intra-frame prediction modes. This predetermined set of possible intra-frame prediction modes requires in the encoding process a number of bits to be coded when an intra-frame prediction mode from the predetermined set of possible intra-frame prediction modes is to be stored or transmitted to the decoding process.
The number of bits necessary to encode intra-frame prediction modes is determined by the number of possible intra-frame prediction modes. In many cases, not all possible intra-frame are needed to produce accurate or acceptable prediction results. Thus encoding bits are wasted on encoding intra-frame prediction modes resulting in identical or similar predictions, i.e. predicted blocks. It is therefore an object of the present invention to reduce the bit capacity required to encode intra-frame prediction modes.